Many vehicles, such as ambulances, define an interior space accessed from exterior the vehicle through an opening. In the case of an ambulance, the opening is typically at the rear of the ambulance and extends both in width and height a dimension close to the dimensions of the ambulance itself in order to provide easy access for patients on a stretcher, the emergency technicians and others. Of course, this opening is normally closed by the ambulance doors, permitting the climate of the interior space to be cooled or heated by the ambulance air conditioner or heater as the weather dictates. Unfortunately, the ambulance doors are often left open when picking up a patient at a residence or accident site and when delivering the patient to the hospital or doctor's office. When the doors are left open, the ambulance air conditioning or heating is typically not capable of delivering the desired comfort as the conditioned air simply flows to the outside through the opening. By failing to maintain the desired comfort level, all personnel in the ambulance suffer, and the patient's health may even be adversely impacted. Even if the climate can be maintained with the doors open, much energy is wasted, increasing fuel consumption and pollutants. A need exists to more efficiently maintain the desired climate in the interior space.